Rectal Evacuation Disorders are Associated With Poor Bowel Preparation in Patients With Chronic Constipation: Results From Two Centers.

Introduction We evaluated factors that can predict the adequacy of bowel preparation in patients with chronic constipation undergoing colonoscopy. Materials and methods We identified patients with chronic constipation who underwent anorectal manometry and at least 1 colonoscopy at 2 tertiary referral centers from 2003 to 2019. We also identified a subgroup of patients who underwent colonic transit testing through radiopaque marker testing. We determined demographic, medical, and constipation-related factors associated with poor bowel preparation and their effect on standardized quality metrics using univariate and multivariate analyses. Results We identified 274 patients with chronic constipation who underwent anorectal manometry testing. Both outlet dysfunction (prolonged balloon expulsion) and slow-transit constipation were associated with suboptimal bowel preparation. Outlet dysfunction was also associated with decreased cecal intubation rates, adenoma detection rates, and sessile serrated polyp detection rates. In multivariable analyses controlling for demographics and known factors associated with poor bowel preparation, outlet dysfunction was associated with an almost 3-fold odds of suboptimal bowel preparation [odds ratio (OR): 2.9; 95% confidence interval (CI): 1.6-5.1] and a 3-fold reduction in cecal intubation rates (OR: 0.3; 95% CI: 0.1-0.8). Among those with radiopaque marker colonic transit testing available, slow-transit constipation was associated with a >2-fold odds of suboptimal bowel preparation (OR: 2.2; 95% CI: 1.1-4.4). Conclusions Among a cohort of patients with chronic constipation undergoing colonoscopy, outlet dysfunction was associated with suboptimal bowel preparation and other quality metrics. Constipated patients with a rectal evacuation disorder may represent a subgroup of patients that could benefit from individualized strategies for better bowel preparation.